| Objectives:1. To establish the cuprizone model of schizophrenia, investigate the schizophrenia-likebehaviors, and study the expressive changes of myelin-associated proteins and Notchsignaling molecules in the brain.2. To observe the effects of quetiapine on schizophrenia-like behaviors of cuprizonetreated mice and the expression of myelin-associated proteins as well as Notchsignaling molecules of cuprizone-treated mice, to explore whether thepro-oligodendrogenesis effects of quetiapine are mediated by Notch signalingpathway.Methods:The study was composed of2parts. Experiment1of the research mainly focus on theinfluence of quetiapine on cuprizone (CPZ) induced schizophrenia-like behaviors ofC57BL/6mice and the expression of brain myelin-associated proteins (mainly refer to themyelin basic protein, MBP and2’,3’-Cyclic-nucleotide3’-phosphodiesterase, CNPase), Notch1receptor and its downstream effector, Hes1. Experiment2of the researchinvestigated the changes of schizophrenia-like behaviors and whole brain expression ofMBP, Hes1and Hes5when MW167, a γ-secretase inhibitor of notch signaling, wasadministrated intraventricularly.In Experiment1, C57BL/6mice were divided into four groups:(1) control group, inwhich mice were normally fed for6weeks,(2) quetiapine group, in which mice werenormally fed and at the same time treated with quetiapine for6weeks,(3) cuprizone group,in which mice were treated with cuprizone for6weeks, and (4) cuprizone plus quetiapinegroup, in which mice were treated with cuprizone and quetiapine at the same time for6weeks. In Experiment1, we observed the following parameters, included:1. Behaviors inthe open field test, elevated plus maze test, Y-maze test, three-chamber paradigm test andnest building test.2. The expression of MBP and CNPase.3. The expression and mRNAabundance of Notch1and Hes1.In Experiment2, C57BL/6mice were divided into six groups:(1) control group, inwhich mice were normally fed for6weeks,(2) quetiapine group, in which mice werenormally fed and at the same time treated with quetiapine for6weeks,(3) cuprizone group,in which mice were treated with cuprizone for6weeks,(4) cuprizone+quetiapine group,in which mice were treated with cuprizone and quetiapine at the same time for6weeks,(5)control+MW167group, in which mice underwent the brain ventricular cannulaimprementation surgery, recovered to normal conditions for1week and begin to benormally fed for6weeks, and during the6th week anesthetized and injected with MW167once a day for7days,(6) cuprizone+quetiapine+MW167group, in which miceunderwent the brain ventricular cannula imprementation surgery, recovered to normalconditions for1week and begin to be treated with cuprizone together with quetiapine for6weeks, and during the6th week anesthetized and injected with MW167once a day for7days. The observation parameters of Experiment2included:1. Behaviors in the open fieldtest, Y-maze test and three-chamber paradigm test,2. The expression of MBP, Hes1andHes5in the brain.Results： We found from Experiment1that, with the down-regulation of MBP, CNPase, Notch1and Hes1, the mice treated with cuprizone exhibited schizophrenia-like behaviors.Co-administration of quetiapine reversed the schizophrenia-like behaviors induced bycuprizone and upregulated the expressions of MBP, CNPase, Notch1and Hes1. Thespecific results are as follows.1. The CPZ treated mice showed reduced ambulatory activities, central time andcentral distance (%) compared with control group (P <0.01) in the open field test, andthey spent much less time staying in the center of the test paradigm instead of theperipheral region (P <0.01). In the elevated plus maze test, the total crosses, open armscrosses (%) and open arms dwelling (%of total time) were significantly increased in theCPZ group, compared with control group (P <0.01). And the CPZ group mice alsoshowed a decrease in the percentage of alteration in the Y-maze test (P <0.01). In thethree-chamber paradigm test, the CPZ group mice didn’t show a preference for theconspecific mouse than an inanimate object (the empty wire cup) in experiment session1,and showed greater preference for a familiar mouse than a novel one in experiment session2(P <0.01). Compared with the control group, the CPZ mice also scored less in thenest-building test (P <0.01). The Western blot results showed a decrease of the MBP andCNPase expression of the CPZ treated mice compared with the control group (P <0.05).The immunofluorescent staining result implied a loss of MBP in the cortex and corpusstriatum of cuprizone treated mice (P <0.01). The Western blot and RT-PCR tests alsoindicated a decrease of Hes1translation and a decreased Notch1and Hes1transcriptionin the brains of CPZ treated mice, respectively (P <0.05).2. Mice of the CPZ+quetiapine group showed an increase in ambulatory activities,central time and central distance (%) compared with CPZ group (P <0.05) in the openfield test. In the elevated plus maze test, the total crosses, open arms crosses (%) and openarms dwelling (%of total time) were significantly decreased in the CPZ+quetiapinegroup, compared with CPZ treated mice (P <0.01). Compared with CPZ group, the CPZ+quetiapine group mice also showed an increase in the percentage of alteration in theY-maze test (P <0.01). And in the three-chamber paradigm test, the CPZ+quetiapine group mice showed a greater preference for an unfamiliar conspecific mouse than aninanimate object (the empty wire cup) in experiment session1(P <0.01), and greaterpreference for a novel mouse than an already familiar one in experiment session2(P <0.01). The CPZ+quetiapine mice also gained a higher score in the nest-building testcompared with the CPZ group (P <0.01). The Western blot results showed an increasedexpression of the MBP and CNPase proteins in the brain of the CPZ+quetiapineco-administrated mice, compared with that of the CPZ treated ones (P <0.05). Theimmunofluorescent staining result indicated that the expression of MBP in the cortex andcorpus striatum of the CPZ+quetiapine co-administrated mice were upregulated (P <0.05). Compared with the CPZ group, the translation of Hes1and transcriptions of Notch1and Hes1were also increased in the brains of CPZ+quetiapine group mice, as wereindicated by Western blot and RT-PCR tests, respectively (P <0.05).We found from Experiment2that, with the down-regulation of MBP, Hes1and Hes5, the mice treated with cuprizone exhibited schizophrenia-like behaviors.Co-administration of quetiapine reversed the schizophrenia-like behaviors induced bycuprizone and upregulated the expressions of aforementioned molecules. When MW167was administrated for7days, the expression of MBP, Hes1and Hes5in the brain weredownregulated and the oligodendrogenesis and antipsychotic effects of quetiapine weretotally blocked. The specific results are as follows.1. The CPZ group, CPZ+Quetiapine group, control+MW167group and CPZ+Quetiapine+MW167group mice all showed reduced ambulatory activities comparedwith control group (P <0.01) in the open field test, and they spent much less time andmoved less distances in the center of the test paradigm instead of the peripheral region (P<0.01). In the Y-maze test, the CPZ group and CPZ+Quetiapine+MW167group miceall showed a decreased alteration rates (P <0.05). In the three-chamber paradigm test, theCPZ group and CPZ+Quetiapine+MW167group mice didn’t show a preference for theconspecific mouse than an inanimate object (the empty wire cup) in experiment session1,or a preference for the unfamiliar stranger2than stranger1in session2. The Western blotresults showed a decrease of the expression of Hes1, Hes5and MBP in the CPZ group mice (P <0.05). The immunofluorescent staining result implied a loss of MBP in thecortex, cingulum bundle, and corpus striatum of cuprizone treated mice (P <0.01).2. Mice of the CPZ+quetiapine group showed an increase in ambulatory activities,central time and central distance (%) compared with CPZ group (P <0.05) in the openfield test. In the Y-maze test, the CPZ+quetiapine group mice showed an increase in thepercentage of alteration (P <0.01). And in the three-chamber paradigm test, the CPZ+quetiapine group mice showed a greater preference for an unfamiliar conspecific mousethan an inanimate object (the empty wire cup) in experiment session1(P <0.05), andgreater preference for a novel mouse than an already familiar one in experiment session2(P <0.05). The Western blot results showed an increased expression of Hes1, Hes5andMBP in the brain of the CPZ+quetiapine co-administrated mice, compared with that ofthe CPZ treated ones (P <0.01). The immunofluorescent staining result indicated that theexpression of MBP in the cortex, cingulum bundle, and corpus striatum of the CPZ+quetiapine co-administrated mice were upregulated to a normal level (P <0.01).3. Compared with the CPZ+Quetiapine group, the total distance traveled, centraltime and central distance (%) of the CPZ+Quetiapine+MW167group all droppeddramatically (P <0.05). In the Y-maze test, the CPZ+quetiapine+MW167group miceshowed a decreased percentage of alteration rates (P <0.05). In the three-chamberparadigm test, the CPZ+quetiapine+MW167group mice showed no preference forstranger1or the empty wire cup in experiment session1, and showed greater preferencefor stranger1than stranger2in experiment session2(P <0.05). The Western blot resultsshowed a decreased expression of Hes1, Hes5and MBP in the brain of the CPZ+quetiapine+MW167group mice (P <0.01). The immunofluorescent staining resultindicated that the expression of MBP in the cortex, cingulum bundle, and corpus striatumof the CPZ+quetiapine+MW167group mice were again downregulated greatly (P <0.01).Conclusion：Cuprizone inhibited the Notch signaling pathway in the brain, impaired myelin andoligodendrocytes, and caused schizophrenia-like behaviors. The atypical anti-psychotic drug, quetiapine activated the Notch signaling in the brain, up-regulated brain MBP,CNPase expression and ameliorated the schizophrenia-like behaviors of CPZ group mice.Blockade of Notch signaling pathway with γ-secretase inhibitor MW167canceled theantipsychotic and pro-myelination effects of quetiapine. The pro-oligodendrogenesis andantipsychotic effects of the atypical anti-psychotic drug quetiapine are mediated byactivation of the Notch signaling pathway. |
PDF Full Text Request